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                [Wf2016]Branch Assignment                </h1>
                <p>时间限制：30s&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;  空间限制：128MB</p>			</div>
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                                <h3>题目描述</h3><p><div>要完成一个由s个子项目组成的项目，给b(b&gt;=s)个部门分配，从而把b个部门分成s个组。分组完成后，每一组的任</div>
<div>意两个点之间都要传递信息。假设在(i,j)两个点间传送信息，要先把信息加密，然后快递员从i出发到总部，再加</div>
<div>密，在到j点。出于安全原因，每次只能携带一条消息。现在给出了道路网络、各个部门和总部的位置，请输出快</div>
<div>递员要走的最小总距离。</div>
<div></div>
<p></p></p><hr/><h3>输入格式</h3><p><div>第一行包含四个整数n,b,s,r。n(2&lt;=n&lt;=5000)代表路口数，b(1&lt;=b&lt;=n-1)是部门数，s(1&lt;=s&lt;=b)是子项目数</div>
<div>r(1&lt;=r&lt;=50000)是道路数。路口标号为1~n，部门在路口1~b，总部在路口b+1。</div>
<div>接下来r行每行三个整数u,v,l，描述一条从u到v长度为l(0&lt;=l&lt;=10000)的双向边。保证没有重边，保证图强连通。</div></p><hr/><h3>输出格式</h3><p><p>&nbsp;输出快递员要走的最小总距离。</p></p><hr/><h3>样例输入</h3><pre>5 4 3 8
1 5 15
5 1 15
2 5 2
5 2 3
3 5 1
5 3 1
4 5 2
5 4 0
</pre><hr/><h3>样例输出</h3><pre>4</pre><hr/><h3>提示</h3><p>没有写明提示</p><hr/><h3>题目来源</h3><p>鸣谢Yts1999上传，lbn187提供译文</p>
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